05. Multiply Big Number

package DPM;

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String num = scan.nextLine();
        int mult = Integer.parseInt(scan.nextLine());
        if (mult==0){
            System.out.println(0);
        }else {
            int rem = 0;
            List<Integer> result = new ArrayList<>();
            for (int i = num.length()-1; i >=0; i--) {
                int res = (num.charAt(i) -'0') * mult;
                res += rem;
                rem = res / 10;
                result.add(res % 10);
            }
            if (rem != 0){
                result.add(rem);
            }
            for (int i = result.size()-1; i >=0 ; i--) {
                System.out.print(result.get(i));

            }
            System.out.println();
        }
    }
}